Colorants are widely used in many applications to provide useful and aesthetic appearance to articles and printed images. Standard colorants can most often be classified as either pigments or dyes. Although such colorants can be directly mixed into an article of manufacture, it is often desirable to prepare ink compositions containing colorants for printing of color images. Such ink compositions typically include a liquid vehicle such as an appropriate solvent containing the dye or the pigment. Dye-based inks generally use a colorant that is soluble in the given liquid vehicle. Conversely, pigmented inks typically use an insoluble dispersed solid colorant to achieve color.
Dye and pigment colorants each have certain properties which are beneficial in certain circumstances and can provide predetermined color properties to a printed image. However, each of dye and pigment colorants also have various limitations and drawbacks which present unique challenges. Specifically, dye colorants exhibit good chroma and long-term stability in solution. However, dye colorants also tend to have poor waterfastness, lightfastness, and smear resistance. In contrast, pigment colorants typically have good waterfastness, good lightfastness, and good smear resistance. Unfortunately, pigment colorants also tend to have limited chroma and a myriad of issues related to maintaining the pigment particles dispersed in solution. Thus, pigment particles of pigment inks can often settle over time.
Consequently, the choice of dye and pigment colorants for use in any particular application is often constrained to these limitations and a wide variety of chemical and physical mechanisms are used to minimize these constraints in a particular commercial product. Accordingly, investigations continue into developing better colorants and ink formulations.